(a) Field of the Invention
The present invention relates to a method and a device for applying and releasing the brakes of a two-wheeler which enable a pair of the right and left shoes to set back reliably from the rim of a wheel when the brakes are released.
(b) Description of the Prior Art
There are known, as the brakes for a two-wheeler such as a bicycle, a side-pull type brake, a center-pull type brake and a cantilever type brake. In any of these types, the brake comprises a pair of arms which is pivotally mounted on the attaching bolt, a pair of shoes mounted on the distal end portion of each of the arms, a brake lever, and a brake wire whose one end is connected to one of the arms and the other end connected to the brake lever. The pair of arms is normally energized to take an unactuated position. The application or release of the brakes are effected via the operation of the brake lever to rotate (or swing) via the brake wire the pair of arms around the attaching bolt thereby to cause the displacement of the pair of brake shoes, i.e. moving the shoes toward the rim of a wheel to pressingly hold both sides of the rim between the pair of the shoes thereby applying the braking of the two-wheeler, or moving the shoes to set back from both sides of the rim of the wheel thereby releasing the braking of the two-wheeler. It is preferable in order to achieve an effective braking to make the distance between the forward surface of each of the brake shoes and each side of the rim facing to each of the brake shoes as equal as possible before actuating the braking operation.
Accordingly, the braking device is conventionally installed to a bicycle, in such a process that an attaching bolt for pivotally mounting the brake arms is first fixed to a frame of the bicycle such that each of the brake shoes is kept apart at a prescribed distance from the rim, and then the brake wire is fastened to the brake arm.
However, in the case of the center-pull type brake or the cantilever type brake, each of the arms is separately secured to the frame of the bicycle, and then connected to a brake wire, so that it is rather difficult to set both of the right and left brake shoes in equidistance to the side surfaces of the rim.
In contrast, in the case of the side-pull type brake, it is rather easy to uniformly set the left and right arms. Actually, however, it is often unavoidable to cause a nonuniformity between the distance from the tip surface of left brake shoe to one side of the rim, and the distance from the tip surface of right brake shoe to the other side of the rim. In order to correct this nonuniformity, it has been conventionally conducted to readjust the distances from the tip surfaces of right and left brake shoes to the sides of the rim by forcefully deforming part of a spring attached to the arms thereby adjusting the restoring or repulsing force of the spring.
However, since the repulsing force of the spring is acted separately on each of the arms, any difference in repulsing force of the spring that will be applied to the left and right arms will invite a situation at the time of effecting the braking that the brake shoe which is mounted on an arm energized weakly by the spring first moves later to the rim, and then the brake shoe which is mounted on an arm strongly energized by the spring moves to the rim. In this manner, the pair of the shoes are successively contacted to the rim thereby holding the rim from both sides.
At the time of releasing the braking on the contrary, the brake shoe which is mounted on an arm strongly energized by the spring is first set back from the rim, and then the brake shoe which is mounted on an arm weakly energized by the spring is set back later from the rim.
Accordingly, if the restoring of one of the arms is fairly weak, the brake shoe which is mounted on this arm is hardly set back from the rim, but remains as being contacted to the rim, thereby causing the generations of frictional noise, increasing the load on the wheel or giving rise to other troubles during ordinary running of the wheeler.